This invention relates to a device for controlling weft yarn insertion, or a warp stop motion device, for use in continuous weft feed looms, without shuttles.
The purpose of the device according to the invention is to stop the loom and emit a corresponding signal, not only each time there is a breakage or absence of a weft yarn -- which is already efficiently obtained by various known devices -- but also whenever the undesired insertion of double wefts occurs.
It is known that, in loom operation, the weft yarn often breaks or is missing, and, to overcome this phenomenon, warp stop motion devices are used for controlling the breakage of the weft thread, in various universally known mechanical, electrical or electronic versions. It can however also happen that, especially with hairy yarn, the weft yarn presented to the gripper of a shuttleless loom takes along with it another weft yarn, which is thus simulaneously inserted, with serious damage to the fabric. This phenomenon is favoured by the fact that the weft yarns ready to be inserted are subjected to very low stretching and, thus, the action of the yarn fluff is sufficient to hook two yarns together.
It can also happen that the perforated tape, controlling weft insertion by means of the presenting device, may get damaged, in which case, one or more wrong wefts will be presented to the gripper in addition to the required weft yarn. In this case, as the perforated tape is generally in the form of an endless loop, the error becomes cyclic with serious damage to the fabric.
The invention relates therefore to an electronic control device being adapted, at each weft insertion, to check the number of wefts being inserted or the possible breakage of the wefts, and to immediately stop the loom -- in the event or irregularities -- in sufficient time to repair the damage, hence representing considerable progress over the known art.